Survival of Ralstonia solanacearum biovar 2 in soil under different cropping systems

Abstract

Survival of Ralstonia solanacearum biovar 2 (race 3) was monitored in an artificially infested field over a five year period. Four cultural practices (maize monoculture, potato monoculture, bare fallow and weed-fallow) were applied. Ralstonia populations in the soil were quantified by planting potatoes in sub-plots of all treatments after a three-year and five-year cropping sequence. In the potato monoculture plots 88% and 96% of the plants wilted after three and five year cycles respectively. The pathogen's ability to survive without the presence of a host was demonstrated by the high wilt index recorded in the fallow plots (58% and 42%). After five years of maize monoculture 40% of potato plants wilted. Less wilting occurred in weed-fallowed plots (31% and 27%), even though some host species were present. Survival of this organism in the soil of all treatments exceeded the twoyear period generally believed to be sufficient for eradication.Oorlewing van Ralstonia solanacearum bioVar2. in grond onder verskillende verbouingstelsels Grondoorlewing van die organisme wat bakteriese verwelksiekte by aartappels veroorsaak, Ralstonia solanacearum biovar 2 (ras 3) is ondersoek in 'n veldproef. Vier verbouingstelsels (mielies in monokultuur, aartappels in monokultuur, kaal-braak en ouland met onkruid hergroei) is toegepas. Na drie en vyf jaar onderskeidelik is subpersele op al die persele met aartappels beplant. Die persentasie plante met sigbare verwelksimptome in die aartappelpersele was 88% na drie jaar en 96% na vyf jaar onderskeidelik. Die patogeen se vermoe om te oorleef in die afwesigheid van 'n gasheer blyk uit die hoe persentasie verwelking van die toetsplante op die kaal-braak persele, naamlik 58% na drie jaar en 42% na vyf jaar. Na vyf jaar van mielie monoku!-tuur het 40% van die toetsplante steeds verwelk. Minder verwelking het voorgekom op die persele waar onkruid toegelaat is (31 % en 27% onderskeidelik) ten spyte van die feit dat sommige van die onkruidspesies bekende gashere is. Oorlewing van Ralstonia in die grond van al die behandelings vir minstens vyf jaar dui daarop dat die aanname in die praktyk dat 'n twee jaar wisselbou-periode voldoende is vir die vernietiging van die organisme, foutief is.

Epidemiological evidence for the emergence of a new pathogenic variant of Ralstonia solanacearum in Martinique (French West Indies)

“…This is apparently the first study to assess the effect of cropping systems on the distribution and composition of field populations of R. solanacearum . Studies dealing with the effect of previous crops on soil populations of R. solanacearum (Michel et al ., 1996; Stander et al ., 2003), or monitoring the population dynamics of R. solanacearum isolates in the rhizosphere of host plants (Melo et al ., 1999), only considered quantitative changes in bacterial populations, rather than the possible shift of the populations’ genetic composition and structure in relation to pathotype and genotype.…”

Survival of Klebsiella pneumoniae strain borkar in pomegranate orchard soil and its tolerance to temperature and pH

“…The plant pathogenic soil bacteria are known to survive in the infected soil samples for various durations. Ralstonia solanacearum survive in soil for up to 2 years, 2 Erwinia caratovora survive in soil for one and a half years 3 while Clavibacter michiganensis survive in soil for 2 years. 4 The plant pathogenic Klebsiella pneumoniae survive in pomegranate orchard soil for more than two years in an infectious stage.…”

On the assessment of the sources of inoculum of bacterial wilt in Brazil

“…However, survival of Ralstonia spp. can vary as reported by Stander et al (2003). Bacterial wilt developed in crops established in fields kept without plants (fallow) for five years (Stander et al 2003).…”